diff --git a/ipynb/SpellingBee.ipynb b/ipynb/SpellingBee.ipynb
index 12fdbd0..5f99ede 100644
--- a/ipynb/SpellingBee.ipynb
+++ b/ipynb/SpellingBee.ipynb
@@ -30,7 +30,7 @@
     "\n",
     "Since the referenced [word list](https://norvig.com/ngrams/enable1.txt) came from *my* web site (I didn't make up the list; it is a standard Scrabble word list that I happen to host a copy of), I felt somewhat compelled to solve this one. \n",
     "\n",
-    "This puzzle is  different from other word puzzles because it deals with *unordered sets* of letters, not *ordered permutations* of letters. That makes things easier. When I searched for an optimal 5 by 5 Boggle board, I couldn't exhaustively try all $26^{(5\times 5)} \\approx 10^{35}$ possibilites; I could only do hillclimbing to find a local maximum. But for Spelling Bee, it is feasible to try every possibility and get a guaranteed highest-scoring honeycomb. Here's a sketch of my approach:\n",
+    "This puzzle is  different from other word puzzles because it deals with *unordered sets* of letters, not *ordered permutations* of letters. That makes things easier. When I searched for an optimal 5 by 5 Boggle board, I couldn't exhaustively try all $26^{(5\\times 5)} \\approx 10^{35}$ possibilites; I could only do hillclimbing to find a local maximum. But for Spelling Bee, it is feasible to try every possibility and get a guaranteed highest-scoring honeycomb. Here's a sketch of my approach:\n",
     " \n",
     "- Since order and repetition don't count, we can represent a word as a **set** of letters, which I will call a `letterset`. For simplicity I'll choose to implement that as a sorted string (not as a Python `set` or `frozenset`). For example:\n",
     "      letterset(\"GLAM\") == letterset(\"AMALGAM\") == \"AGLM\"\n",